1. Field of the Invention
The present invention relates generally to a rover and base smart antenna system for global navigation satellite systems (GNSSs). Applications include vehicle guidance in real-time kinematic (RTK) and other modes, geographic information systems (GIS), mapping and survey. A weatherproof enclosure is provided for the exposed system components.
2. Description of the Related Art
Movable machinery, such as terrestrial agricultural equipment, agricultural aircraft, open-pit mining machines, earth moving equipment and the like, and vehicles generally, can benefit from accurate GNSS-based guidance and control. For example, satellite positioning systems (SATPS) are extensively used in agriculture for guiding parallel and contour swathing and controlling agricultural equipment through various operations, including precision farming. In order to define swaths across a field (in farming, for example), the guidance system collects positions of the vehicle as it moves across the field. When the vehicle commences the next pass or swath through the field, the guidance system offsets the collected positions for the previous pass by the width of the equipment (i.e. swath width). The next set of swath positions is used to provide guidance to the operator as he or she drives the vehicle through the field.
The current vehicle location, as compared to the desired, swath-defined vehicle location, can be relatively accurately determined with GNSS-based positioning and provided to the vehicle's operator and/or to a vehicle's steering system as an “offset” and a steering heading. The SATPS provides the 3-D location of signal reception at the antenna, which can be defined with geodesic coordinates used by GNSS for positioning and guidance. A common approach to improve accuracy and correct errors caused by losing signal from one or more satellites is to use a remotely located base station receiver/transmitter and a mobile rover receiver/transmitter combination to provide differential GNSS (DGNSS/DGPS) guidance data. The base station is placed at a known location, and will also receive satellite positioning data. Because the base station is at a known location, corrections can be applied to the satellite position data and then transmitted to the mobile antenna and receiver. This position correction can then be applied to the mobile tracking system for a more precise position fix.
GNSS includes the Global Positioning System (GPS), which was established by the United States government and employs a constellation of 24 or more satellites in well-defined orbits at an altitude of approximately 26,500 km. These satellites continually transmit microwave L-band radio signals in three frequency bands, centered at 1575.42 MHz, 1227.60 MHz and 1176.45 MHz, denoted as L1, L2 and L5 respectively. All GNSS signals include timing patterns relative to the satellite's onboard precision clock (which is kept synchronized by a ground station) as well as a navigation message giving the precise orbital positions of the satellites. GPS receivers process the radio signals, computing ranges to the GPS satellites, and by triangulating these ranges, the GPS receiver determines its position and its internal clock error. Different levels of accuracies can be achieved depending on the techniques employed.
GNSS also includes Galileo (Europe), the GLObal NAvigation Satellite System (GLONASS, Russia), Beidou (China), Compass (proposed), the Indian Regional Navigational Satellite System (IRNSS) and QZSS (Japan, proposed). Galileo will transmit signals centered at 1575.42 MHz, denoted L1 or E1, 1176.45 denoted E5a, 1207.14 MHz, denoted E5b, 1191.795 MHz, denoted E5 and 1278.75 MHz, denoted E6. GLONASS transmits groups of FDM signals centered approximately at 1602 MHz and 1246 MHz, denoted GL1 and GL2 respectively. QZSS will transmit signals centered at L1, L2, L5 and E6.
Other GNSS applications include geographical information system (GIS), such as mapping and surveying. Still further, machine control with GNSS enables precision control of various types of equipment in agriculture, mining, construction, transportation and other operations. GNSS receivers typically require clear views of the sky (i.e. satellite constellations) for ranging signal reception. The antennas are commonly mounted externally to the vehicles and equipment, and are thus exposed to the elements. Weatherproofing external GNSS components is an important design objective.
Many DGNSS systems require an antenna and receiver rover unit on the vehicle being tracked, as well as an antenna and a receiver base unit placed at the base station. The use of a separate receiver and antenna unit requires power to be provided to two units, requires separate housings for each unit, and requires compatibility between the receiver and the antenna. The need for separate receiver and antenna units can increase costs and decrease efficiency.
Heretofore there has not been available an enclosed rover and base antenna system with the advantages and features of the current invention.